Process for manufacturing hydrocarbon oils



May 10, 1938. F, E FREY ET AL 2,116,723

PROCESS FOR MANUFACTURING HYDROGARBON OILS Filed Feb. 20, 1956FR'EDERICK E. FRI-:Y HARQLD J. HEPP ATTORNEYS.

Patented May 10, 1-938 PROCESS FOR MANUFACTURING HYDRO- cmo N OILSFrederick E. Frey and Harold J. Hepp, Bartlesville, `kla., assignors toPhillips Petroleum Company, a corporation ot Delaware ApplicationFebruary 20, 1936, Serial No. 64,972

' 9Claims.

This invention relates to the manufacture of volatile hydrocarbon oilsand in particular to the manufacture of oils highly branched instructure and peculiarly suitable for motor fuel in an 5 internalcombustion engine where parafiinic characteristics and high antiknockvalue are important. It has been proposed to produce normally liquidvolatile hydrocarbons suitable for motor fuel by subjecting normallygaseous hydrocarbons to heat and pressure and thereafter separating fromthe products of reaction such hydrocarbon products and also the gaseoushydrocarbons suitable for returning to the conversion operation.

-We have discovered that if from a mixture of gaseous hydrocarbons thereis separated a material consisting of isobutane, or predominating inisobutane, that such a fraction, exposed to suitable conditions of heatand pressure to be set forth, can be converted into volatile normallyliquid hydrocarbons almost entirely aliphatic and largely of branchedstructure. We have discovered that a product of this character is notobtained under conditions of low pressure and with extensive conversionof isobutane in a single thermal treatment which, from the standpoint ofeconomy in conversion alone, is desirable. In our invention we producevolatile normally liquid hydrocarbons largely aliphatic and of branchedstructure by subjecting isobutane to a tempera- Yture within the range752 to 1292 F., within which range cracking takes place, whilemaintaining a pressure of at leastl 500 pounds per square inch.

It is of the essence of 35.. this invention that the to 50 per cent orless of the isobutane content of the material subjected t'o theconversion step in order that products of the aliphatic characterdescribed be obtained, and further that an elevated pressure must bemaintained of at least 500 pounds per square inch during the conversionand i preferably higher pressures, the higher the bet'- ter, thepressure being limited only by the strength of the apparatus. Isobutanesurviving the thermal treatment may be returned to the conversion stepto be subjected again to treatment along with fresh isobutane-richmaterial. Butylenes occurring in the eiuents from the thermal treatment,as well as any desired fraction of the propane and propylene, may alsobe returned for retreatment. In this way recycle operation in which allsuitable hydrocarbons are treated will always call for the return vof avolume of stock approximately equal to, or greater than, the volume offresh hydrocarbon to be subjected tothe process. The fresh hydrocarbonstock to be subjected to conversion should contain preferably a. highercontent of isobutane than is found ink hydrocarbons extracted fromvnatural extent of decomposition of isobutane be limited gas or from thegas derived from oil cracking stills and should contain accordingly atleast 50 per cent of isobutane, but the higher the isobutane content upto l0() per cent the more highly branched will be the structure of thenormally liquid hydrocarbons produced and the more ef-` i'ciently willthey perform in internal combustion engines of high compression ratio.

The time during which the hydrocarbon should be exposed to a conversiontemperature is determined by the restriction that at least 50 per centof the isobutane survive the thermal treat ment and the time of reactionwill consequently be decreased with elevation of the temperatureemployed and will be of the order of 0.2 to l minute at about 1.050 F. Alower extent of destruction of the isobutane during the thermaltreatment Will increase the proportion of branched aliphatichydrocarbons in the normally liquid products but an extent ofdecomposition of isobutane much below 10 per cent will result in a smallproduction of normally liquid products and an attendant increasedexpense.

The figure which forms a part of this specification diagrammaticallyillustrates one form of apparatus for practicing this present invention.

A hydrocarbon mixture containing isobutane is subjected to fractionaldistillation in fractionating element (I) and a concentrate high inisobutane passes through conduit (2) to pump (3) wherein the pressure israised to the desired pressure for the conversion. From the pump thesaid hydrocarbon fraction passes through a tube coil situated within thefurnace (5) wherein the hydrocarbon passing continuously through thetube coil may be subjected to the desired pyrolysis temperature for thedesired time. The thermally treated hydrocarbon passes through conduit(6) and heat exchanger (l) wherein a part of the heat may be extracted,to fractionating column (8) wherein said thermally treated hy ocarbo isseparated into a fraction composed rimarilymf normally liquidhydrocarbons and a fraction composed of gaseous hydrocarbons. The firstmentioned fraction'is passed through conduit (9) to` fractionatlngcolumn (I0) wherein hydrocarbons boiling above the desired range areseparated from the -mixture and removed through conduit (il), while thevolatile normally liquid hydrocarbon product is isolated and withdrawnthrough conduit (I2) and collected in the container (I3). The gasespassing from fractionating column (B) through conduit (It) enterseparator (I5) wherein light gases are separated from the mixture anddischarged from the system through conduit A( I6), and normally gaseoushydrocarbons of three and four carbon atoms per molecule containing theunconverted isobutane are returned through conduit (I1) to the inlet ofpump (3).

A further increase in antiknock value of the motor fuel produced isobtained by subjecting the normally gaseous hydrocarbons resulting fromthe thermal conversion to a selective catalytic polymerization wherebythe isobutylene present, which we have found to be formed in substantialamount, is converted into di-polymer and tripolymer which may beincorporated in the hydrocarbon product to increase the antiknock valueboth of the motor fuel as produced thermally and after subjecting it tonon-destructive hydrogenation.

With further reference now to the figure, it will be seen that conduit(I4) includes a valve (I 8), which when closed will allow normallygaseous hydrocarbons owing through conduit (I4) from the fractionatingcolumn (8) to pass into conduit (I9), which is controlled by a valve andin which is provided a pump (2I) to I force the normally gaseoushydrocarbons through a heating element (22) and a polymerizationcatalyst chamber (23). The polymers produced in the chamber (23) arethen passed along with other material present to the chamber (24)wherein unreacted gases are separated and removed throughconduit (25) tothe conduit (I4) so that they may ultimately pass into the separator(I5). Conduit (25) is provided with a valve (26) which will remain openwhen valve (20) is open, and be closed when the valve (I8) is open. Fromthe separator (24) the polymers pass through conduit (21) to thefractionating column (8).

The catalytic polymerization may be effected by a variety of catalystswhich comprise sulfuric acid, phosphoric acid, aluminum chloride, andactivated fullers earth, the polymerization is selective for isobutyleneat temperatures somewhat below those required to polymerize propyleneand butenes. The temperature for such selective polymerization isreadily determined by experiments and usually lies between and 300 F.,the exact temperature depending upon the activity of the catalyst.

The normally liquid hydrocarbon product obtained by the process setforth is predominantly aliphatic but contains small proportions ofolefine hydrocarbons particularly when the lower operating pressures inthe range are employed for the thermal treatment. It is an object of ourinvention to produce a more highly saturated product of more completelyparailinic characteristics by subjecting the said material tonondestructive hydrogenating conditions with the aid of a catalyst. Forthis purpose chromium oxide catalyst (U. S. P. 1,905,383, April 25,1933, Frey and Hnppke) or other catalysts, such. as nickel andmolybdenum sulfide, may be used with elementary hydrogen preferably asthe source of hydrogen though light parafiinic hydrocarbons, preferablybutanes, may be used for the purpose, the hydrogen in such a case beingextracted from the butane with the formation of butylene as a product ofthe process. 'Ihe hydrogen or hydrogen-supplying agent is passedtogether with the normally liquid hydrocarbon product over the catalystat a reaction temperature which will vary widely with the catalystselected, being usually between 200 and 500 F., and from the eilluentsof the catalytic treatment the normally liquid product of saturated typemay be separated.

Non-destructive 'hydrogenation, either of the' polymers from theselective polymerization effected in polymerization catalyst chamber 23,or of the liquid material from the thermal process as eiected in tubecoil 4, or of mixtures of these two, may take place in the followingmanner.

Eluents of the fractionating column (8) passing through conduit (9) arepassed through conduit (30) and valve (3i) and into conduit (32). whilevalve (33) in conduit (9) is closed. Pump (34). in conduit (32)compresses the hydrocarbons to a desired hydrogenating pressule, andforces them to the hydrogenating chamber (35) which contains anysuitable catalyst of the type herein taught. Hydrogen under suitablepressure is introduced into this chamber through conduit (36), andpasses countercurrent to the hydrocarbons being treated therein. Gasescontaining or consisting of excess hydrogen are withdrawn from chamber(35) throughconduit (31). Hydrogenated hydrocarbons are passed from thechamber (35) through conduity (38) and valve (39) and into conduit (9)and then to the frac-- tionating column (I0) for further separation ashas been herein described.

If the process is operated to4 include selective polymerization ofisobutylene, the polymers from polymerization catalyst chamber (23)passing through conduit 21) may be subjected to hydrogenation by passingthem into fractionating colp umn (8) and out conduit (9), however, ifdesired, they need not be passed into the column (8), but may be passedfrom conduit (21) dlrectly into conduit (32) through conduit (40) andvalve (4I), while valve (42) in conduit (21) is closed. If it is desiredto mix the polymers" y from the catalytic polymerization with thehydrogenated hydrocarbons from the thermal treatment, this may be doneby closing both valves (4I and (42) and passing the polymers throughconduit (43) and valve (44) to conduit. (9),

It is also a part of this invention to produce parailn hydrocarbons ofhighly branched structure in concentrated form. This is accomplished bysubjecting the normally liquid product of the thermal treatment, eitherhydrogenated or unhydrogenated, to fractional distillation in emcientapparatus whereby highly branched hydrocarbons, notably isohexanes,isoheptanes and isooctanes, may be obtained in a concentrated form.

A p'araflinic motor fuel may also be obtained without the hydrogenationstep by treating the normally liquid product or fractions thereof with apolymerizing agent such as sulfuric acid or aluminum chloride andremoving heavier polymer so formed by distillation.

CH4 r ...T- C21-I4 CzHs CsHo CaHa CeHa C4H1o Gasoline Tar The normallyliquid products contained 10 per cent of hydrocarbons boiling above 350F. 'I'he u gasoline was found to contain less than 10 per cent of cyclichydrocarbons and to consist of hydrocarbons of 5, 6, 7, and 8 carbonatoms per molecule, present in the following percentages andpredominating in branched parailins:

Cs 23 Cs 15 C7 37 Cs .v 15 Heavier 10 The normally liquid hydrocarbonswith the high boiling material removed, subjected to an engine knocktest, showed a high antiknock rating.

Example 2.--Normally liquid hydrocarbons produced substantially inaccordance with Example 1, except that hydrocarbons of 3 `and 4 carbonatoms per molecule, separated from the products were returned to thethermal treatment accompanied by fresh isobutane, and boiling below 350F. were admixed with ve times their vapor volume of hydrogen and passedover chromic oxide gel catalyst maintained at a' temperature of 642 F.The oleiln content was thereby reduced from 25 per cent to 2 per cent.The engine antiknock test rating was virtually the same as for theproduct in Example 1 but the addition of small amounts of tetraethyllead was found to effect a considerable improvement in knock rating, theaddition of 3 cc. of tetraethyl lead fluid per gallon producing a fuelof 98 octane number, as determined by the A. S. T. M. method D 357-34'1.

Example 3.--Normally liquid hydrocarbons obtained substantially asdescribed in Example 1 were subjected to fractional distillation and thefraction consisting largely of branched heptanes of high antiknock valuewas isolated between 165 and 185 F. distilling temperature (atmosphericpressure) aswell as fractions distilling in the range130 to 146 and 205to 215 F. likewise of high antiknock value and composed predominantly ofisohexanes and iso-octanes respectively.

Having described our invention, what we claim is:

1. A process for producing special motor fuels of high antiknock qualityand consisting predominantly of aliphatic hydrocarbons of branchedstructure, which comprises subjecting a normally gaseous hydrocarbonmixture comprised predominantly of isobutane to thermal treatment at'152 to 1292 F. and at a pressure exceeding 500 pounds per square inchfor such a time as will effect the conversion of no more than 50 percent of the isobutaneinitially present, and then separating from theeiiiuents normally liquid hydrocarbons in the gasoline boiling range.

2. A process lfor producing special motor fuels of high antiknockquality possessing paraiiinic characteristics 'and of special boilingrange, which comprises subjecting a normally gaseous hydrocarbon mixturecomprised predominantly of isobutane to thermal conversion at 752 to1292 F. and at a pressure exceeding 500 pounds per square inch for sucha time as will effect the conversion of no more than 50 per cent of theisobutane initially present to form normally liquid aliphatichydrocarbons, separating said normally liquid hydrocarbons from thethermally converted hydrocarbons, subjecting the said normally liquidhydrocarbons to non-destructive hydrogenation, and finally subjectingthe resulting normally liquid hydrocarbons to fractional distillation toseparate highly branched parailin hydrocarbons in concentrated form foruse as special motor fuels.

3. A process for producing normally liquid hydrocarbons predominantlyaliphatic and of branched structure, which-comprises subjectinghydrocarbons comprised predominantly of isobutane to thermal conversionat '752 to 1292o F. and at a pressure exceeding 500 pounds per squareinch for such a time as will effect the conversion of no more than 50per cent of the isobutane initially present producing normally liquidaliphatic hydrocarbons and normally gaseous hydrocarbons of anappreciable isobutylene content, separating the thermally convertedhydrocarbons into normally liquid hydrocarbons and normally gaseoushydrocarbons, passing the normally gaseous hydrocarbons into contactwith a polymerization catalyst under such conditions that isobutylene isselectively polymerized into aliphatic hydrocarbon polymers in the motorfuel boiling range; separating said polymers from the remaining normallygaseous hydrocarbons and mingling them with said normally liquidhydrocarbons, and separating from said normally liquid hydrocarbons aselected normally liquid hydrocarbon fraction in the motor fuel boilingrange.

4. A process as in claim 3 wherein the mingled normally liquidhydrocarbons are subjected t0 non-destructive hydrogenation, and ahighly parainic, high antiknock motor fuel separated therefrom.

5. A process for the production of special motor fuels containingessentially aliphatic hydrocarbons of branched structure, whichcomprises separating from a normally gaseous hydrocarbon mixture anisobutane fraction comprising isobutane in essentially a pure state,mixing said isobutane fraction with a recycle stock consisting of atleast 50 per cent isobutane and minor portions of other three and fourcarbon atom hydrocarbons, subjecting the mixture to thermal conversionat r152 to 1292" F. and at a pressure exceeding 500 pounds per squareinch for such a time as will effect the conversion of no more than 50per cent, of the total isobutane initially present to form normallyliquid aliphatic hydrocarbons, separating the eilluents into a fractionof normally liquid hydrocarbons and removing same from the process and afraction containing hydrocarbons of three and fewer carbon atoms permolecule and removing this fraction from the process and an intermediatefraction consisting of at least per cent of isobutane and minor portionsof other three and four carbon atom hydrocarbons and returning at leasta portion -of said intermediate fraction as recycle stock to be admixedwith the aforesaid isobutane fraction.

6. A process for the production of special motor fuels essentiallycomposed of selected aliphatic hydrocarbons of branched structure, whichcomprises subjecting hydrocarbons comprised predominantly of isobutaneto thermal conversion at 752 to 1292 F., and at a pressure exceeding2000 pounds per square inch for such a time as will effect theconversion of no more than 50 per cent of the isobutane initiallypresent, producing normally.liquid aliphatic hydrocarbons, andseparating from the eilluents of said conversion a fraction distillingbetween 130 and 215 F.

7. A process for producing special motor fuels inantly of isobutane tothermal treatmentwat '152 to 1292 F. and at a pressure exceeding 500pounds per square inch for such a time as will e'ect the conversion ofbetween 10 and 50 per cent of the isobutane initially present, and thenseparating from the eiiluents normally liquid hydrocarbons in thegasoline boiling range.

8. A process for producing normally liquid hydrocarbons predominantly-aliphatic and of branched structure. which comprises subjectinghydrocarbons comprised predominantly of isobutane to thermal conversionat 752 to 1292" F. and at a pressure exceeding 500 pounds per squareinch for such a time as will effect the conversion of between 10 and 50vper cent of the isobutane initially present producing normally liquidaliphatic hydrocarbons and normally gaseous hydrocarbons of anappreciable isobutylene content, separating the thermally convertedhydrocarbons into normally liquid hydrocarbons and normally gaseoushydrocarbons, passing the normally gaseous hydrocarbons into contactwith a polymerization catalyst under such conditions that isobutyiene isselectively polymerized into aliphatic hydrocarbon polymers in the motorfuel boiling range, separating said polymers from the remaining normallygaseous hydrocarbons and mingling them with said normally liquidhydroarating from a normally gaseous\`` hydrocarbon mixture an isobutanefraction comprising isobutane in essentially a pure state, mixing saidisobutane fraction with a recycle stock consisting of at least 50 percent isobutane and minor portions of other three and four carbon atomhydrocarbons, subjecting the mixture to thermal conversion at 752 to1292 F. and at a pressure exceeding 500 pounds per square inch for sucha time as will eiect the conversion of between 10 and 50 per cent of thetotal isobutane initially present to form normally liquid aliphatichydrocarbons, separating the eiliuents into a fraction of normallyliquid hydrocarbons and removing same from the process and a fractioncontaining hydrocarbons' of three and fewer carbon atoms per moleculeand removing this fraction from the process and an intermediate fractionconsisting of at least 50 per cent of isobutane and minor portions ofother three and four carbon atom hydrocarbons and returning at least aportion of A.said intermediate fraction as recycle stock to be admixedwith the aforesaid isobutane fraction.

FREDERICK E. FREY. HAROLD J. HEPP.

